The wireless 802.11h communication standard, which is an extension of the 802.11a standard, is designed to meet European regulations regarding the use of the 5 GHz band by ensuring that WLAN systems operating in this band do not interfere with military radars and other users of the frequency band. Two mitigation technologies are provided with that purpose in mind:                Dynamic Frequency Selection (DFS):        Transmit Power Control (TPC).        
The previous radar detector implemented in WLAN systems was solely based on the detection (power-wise) of a single short pulse and is expected to yield a relatively high rate of false alarm when performance assessment occurs. This scheme, which comes within the framework of the AGC (automatic gain control) procedure, uses the power measurements provided by the RSSI block to make a decision about whether a short pulse has been received and is likely to trigger upon the reception of any type of pulse-like signal without discrimination (there actually exist radar-like short pulses or bursts, which may result from either external parasitic noise, packet collision from WLAN stations operating in the same channel or WLAN activity in adjacent channels).
The problem to be solved comes within the framework of DFS and is concerned with the successful detection of co-channel radar signals by an 802.11h station in order to prevent any disruptions of the radar station nominal functioning by means of a subsequent channel change.
The radar detection scheme has to be highly reliable, as any false alarm would result in an 802.11h receiver station non-occupying the radar-flagged channel for 30 minutes.
What types of signals should we be able to detect? The military is actually all but generous when it comes to informing the rest of the community about the features of the fancy signals emitted by their radar stations. However, despite the secrecy surrounding military radars, it is generally admitted that radar signals broadly fall into either one of the two following categories:                Pulsed waveforms (pulse repetition frequency), which are made of trains of time-spaced pulses emitted at regular time intervals,        Continuous waves (frequency modulated continuous wave) whose instantaneous frequency varies according to a periodical pattern, the most commonly used one being the linear chirp.        
The ETSI, which has initiated a regulation effort regarding these matters, wrote a document describing certain characteristics of the radar signals encountered in Europe, which actually emphasizes the first category described above. So, as far as we are concerned and as a starting point, we have taken for granted the information provided by the ETSI material we could lay our hands on and have therefore decided to restrict ourselves to the detection of pulse waveforms only. These radar pulses are assumed to:                Be either sinusoidal or chirp-like,        Abruptly start and finish power-wise,        Have a width of either 1 or 2 μs,        Have a repetition rate of either 330, 700 or 1800 per second.        